British Prime Minister David Cameron sent hundreds more troops into northern England on Sunday to help exhausted residents and emergency workers fight back rising river waters that have inundated towns and cities after weeks of heavy rain.

Cameron said the flooding is "unprecedented" and vowed to do everything possible to protect people and their property as the damage spread to the major cities York, Leeds and Manchester. He said protective systems and contingency plans will be reviewed because the frequency of such extreme weather events seems to be on the rise.

Weeks of persistent rainfall has saturated the ground and swollen the rivers to record levels, leaving entire swathes of northern England, and smaller parts of Wales and Scotland, vulnerable. Several hundred flood warnings remain in effect.

There have been no fatalities or serious injuries reported, but hundreds of people have been evacuated from houses and apartments in York, 200 miles (320 kilometers) north of London, where 3,500 properties are judged to be at risk. Emergency crews worked extra shifts to try to restore power to roughly 7,500 blacked out homes in the greater Manchester and Lancashire areas.